The invention relates to an electro acoustic target searching system for torpedos. It is known to provide in the head of the torpedo an electro acoustic transducer. The reception diagram can be tilted mechanically or electrically and automatically with its main sensitivity axis aligns itself to a noise source, usually the propeller of a ship which has to be attacked. For accurate localization of the target and control of the torpedo, the selection of the reception frequency of the transducer is of essential importance. In order to hinder localisation of the torpedo by the enemy the transducer as far as possible only operates passively, that means it only receives noise without itself transmitting sound pulses. During determined intervals of the travel of the torpedo in many cases a temporary active operation of the transducer is favorable. The size of the transducer is limited by the dimensions of the torpedo. The selection of the reception frequency depends on the expected noise spectrum of the target which is to be attached. However, the selection process must also take into account attenuation of sound waves in water which increases rapidly with increasing frequency. For a greatest possible reception range, therefore, an as low as possible reception frequency would be favorable. For achieving a suitable angular solution, however, mechanical dimensions of the transducer would be required which because of the limitations in space within the torpedo cannot be achieved.
A further point of view for the selection of a suitable reception frequency derives from the expected combat situation in which mostly a greater number of targets and therewith a greater number of noise sources are present simultaneously which furthermore by acoustic countermeasures try to hinder localisation. It is the object of the invention therefore to provide an electro acoustic target searching system for torpedos which in optimum manner takes care of the opposing requirements.